Audio Class Microphone - STM32F4 Discovery

I am making a SDR and implementing FM demodulation over it. We chose STM32F4 controllers for our applications yet we are successful in receiving the signal till the DAC's output.

Yet I am still required to make this board more fruitful to us by introducing like a USB Microphone device. It just transmits the data to the host as an audio device just like a microphone do. Please help me in making my project complete. I am using KEIL uVision for ARM.

Are you facing any issue with a code you are already using? Or you need an example?
Did you checked the examples provided within the USB library (Ex: STM32_USB-Host-Device_Lib_V2.1.0\Project\USB_Device_Examples\AUDIO)?